We hypothesize that dyspnea and disability in chronic obstructive lung disease (COLD) is due to inspiratory muscle dysfunction. If so, many patients with severe COLD may have chronic inspiratory muscle fatigue which can be treated by nocturnal ventilatory muscle rest (VMR) and/or inspiratory muscle training (IMT). Furthermore VMR may render the inspiratory muscles more trainable by IMT. Thus, a randomized controlled clinical trial is planned to assess whether nocturnal VMR and IMT either alone or in combination will 1) improve exercise performance; 2) alleviate the sensation of dyspnea; and 3) improve measurable quality of life for patients with severe irreversible chronic obstructive lung disease (COLD0. Patients will be randomized to one of four groups. Group I will act as a control and will receive placebo IMT only. Group II will receive IMT. Group III will receive VMR and placebo IMT, while group IV will receive both VMR and IMT. Respiratory muscles will be rested by use of a cuirasse ventilator. Inspiratory muscle training will proceed by patients breathing through a respiratory line with an appropriate resistance. Throughout enrollment, careful records will be kept of all patients examined. Reasons for exclusions will be noted to allow identification of potential distortions in the study population and to guide appropriate extrapolation. The primary outcome of interest will be the change in exercise tolerance as measured by the endurance time at 2/3 of peak power output. Secondary outcomes, including the distance walked in 12 minutes, level of dyspnea, arterial blood gases, and measurable quality of life, are expected to reflect similar patterns of change. Analysis will compare combined and individual interventions as well as individual interventions and placebo. Based upon preliminary data, from uncontrolled trials, which show substantial improvement resulting from both IMT and VMR we hope to confirm the benefits of these interventions. If successful, these new forms of low-cost therapy may revolutionize the rehabilitation of patients with severe COLD.